This invention relates in general to universal joints, and in particular to an apparatus suitable for cooperating with a half round yoke to retain bearing cups in universal joints.
Universal joints are well known devices which provide a driving connection between two members adapted to rotate about non-aligned axes of rotation. Universal joints are widely used between rotatable drive shaft sections in vehicle drive train systems. A typical universal joint includes a cross having a central body portion with four cylindrical trunnions extending outwardly from the cross. The trunnions are oriented in a single plane and extend at right angles relative to one another, and the trunnions have a common intersection at the center of the central body portion.
A hollow cylindrical bearing cup is mounted on the end of each of the trunnions. Needle bearings or similar means are provided between the outer cylindrical surfaces of the trunnions and the inner cylindrical surfaces of the bearing cups to permit relative rotational movement between the trunnions and the bearing cups. The bearing cups which are mounted on an opposed pair of the trunnions can be connected to a first end yoke secured to an end of a first drive shaft section, while the bearing cups mounted on a second opposed pair of the trunnions can be connected to a second end yoke secured to an end of a second drive shaft section.
Several different types of yokes are used in universal joints. Often the yoke is a full round yoke which is provided with a pair of opposed arms with cylindrical holes in the arms for insertion of the bearing cups. Another common type of yoke is a half round yoke, where each arm forms a curved, usually semi-circular yoke surface for receiving the bearing cup, and a retainer strap is bolted to the yoke to hold the bearing cup in place. Typically, the retainer strap for a half round yoke is provided with a curved inner surface which mimics the cylindrical contour of the bearing cup.
The performance of the retainer strap is important in the overall performance of the universal joint. The retainer strap must be strong enough to withstand the torsional and other forces associated with holding down the bearing cups of the universal joint, and yet be light weight and not bulky. Further, the retainer strap must be of very precise dimensions to assure that the bearing cup does not rotate during operation of the universal joint. A common design for retainer straps to be used with half round yokes is a generally flat plate which is curved at its midsection to conform to the shape of the bearing cup. Bolts are positioned at the end portions of the retainer strap to secure it to the yoke. A problem with conventional retainer straps is that they often exhibit metallic failure at the end portions, where they are bolted to the yoke.
Conventional flat plate retainer straps are usually made by stamping. Stamping stretches the metallic part, so that the precise fit of the bearing cup is not always possible. One known method for assuring the correct size of the opening defined by the retainer strap and the half round yoke is to bolt the retainer strip and the yoke together and mill the opening to its final tolerance. While this assures that the opening is of the correct dimensions, this method requires the extra manufacturing step of milling the opening to the final size. Also, this method creates a matched set consisting of the yoke and retainer strap, and the two parts must be used together. This method does not produce interchangeable retainer straps, and therefore manufacturing costs are increased.
It would be advantageous to provide a half round yoke retainer strap for a universal joint where the retainer strap is simple and inexpensive to manufacture, and yet provides improved strength performance.